The invention relates to a heating system for heating a vehicle interior of a vehicle having an internal combustion engine. The invention also relates to a heating strategy for heating a vehicle interior by using the heating system according to the invention.
It is known that the engine heat is used for heating the vehicle cabin in vehicles having internal combustion engines that are coupled with a heat exchanger of the air conditioner of the vehicle. In hybrid vehicles, an electric drive is used in addition to the internal combustion engine, wherein the internal combustion engine and the electric drive are controlled so as to achieve the most optimal energy efficiency. However, the heat generation of the internal combustion engine is kept low as a result and the engine heat is therefore not always adequate to heat the vehicle interior, so that electric heat sources, for example a high-voltage PTC add-on heater (HV-PTC), are used.
Therefore, heating systems and heating strategies are required for hybrid vehicles that optimally use the available heat sources of the vehicle in terms of energy efficiency and electrical range of the hybrid vehicle.
A generic heating system for a vehicle with an internal combustion engine is known from DE 10 2008 035 955 A1, wherein the internal combustion engine is coupled by way of a coolant inlet and a coolant outlet with a first heat circuit having a heater for the interior of the vehicle. Furthermore, a bypass line of the first heat circuit is provided between the coolant inlet and the coolant outlet of the internal combustion engine for forming a second heat circuit. This bypass line is controlled by a bypass valve and has an electrically or exhaust-gas-heated heat source and a temperature sensor, wherein the heat source and the associated temperature sensor can also be arranged in the first heat circuit in the flow direction upstream of the heater provided for the interior. When a certain temperature is detected at a temperature sensor disposed at the coolant outlet of the engine, an inlet valve at the coolant inlet of the internal combustion engine is opened such that coolant passes through both the internal combustion engine and through the bypass line. This bypass valve is not closed until a thermostat opens a coolant circuit to a vehicle cooler, since otherwise the heat supplied via the additional heat source would be discharged via the coolant circuit to the vehicle cooler. When the internal combustion engine is started, the coolant is fed directly through the bypass line and the additional heat source to the heater for the interior, when the bypass valve is open and inlet valve at the coolant inlet of the internal combustion engine is closed. Thus, coolant will not flow through the heater during a cold start of the engine, while at the same time the coolant is heated by the heat source.
An obvious disadvantage of this known heating system is that the highest possible energy efficiency cannot always be achieved in all operating states of travel when used in a hybrid vehicle.